package engine

// UrgencyCoefficients holds the configurable coefficients for urgency calculation
type UrgencyCoefficients struct {
	Due         float64
	PriorityH   float64
	PriorityM   float64
	PriorityD   float64
	PriorityL   float64
	Active      float64
	Age         float64
	AgeMax      int
	Tags        float64
	Project     float64
	Waiting     float64
	UrgentTag   string  // Configurable urgent tag name (default: "next")
	UrgentCoeff float64 // Coefficient for urgent tag
}

// CalculateUrgency computes the urgency score for a task
func (t *Task) CalculateUrgency(coeffs *UrgencyCoefficients) float64 {
	urgency := 0.0

	// Due date contribution
	urgency += t.urgencyDue(coeffs.Due)

	// Priority contribution
	urgency += t.urgencyPriority(coeffs)

	// Age contribution
	urgency += t.urgencyAge(coeffs.Age, coeffs.AgeMax)

	// Active task contribution
	urgency += t.urgencyActive(coeffs.Active)

	// Waiting task penalty
	urgency += t.urgencyWaiting(coeffs.Waiting)

	// Tags contribution
	urgency += t.urgencyTags(coeffs)

	// Project contribution
	urgency += t.urgencyProject(coeffs.Project)

	return urgency
}

// urgencyDue calculates urgency contribution from due date
// Linear scale: overdue=12.0, today=10.0, 7 days=6.0, 14+ days=2.0
func (t *Task) urgencyDue(coeff float64) float64 {
	if t.Due == nil {
		return 0.0
	}

	now := timeNow()
	due := *t.Due

	// Calculate days until due (negative if overdue)
	duration := due.Sub(now)
	daysUntil := duration.Hours() / 24.0

	var scale float64

	if daysUntil < 0 {
		// Overdue - maximum urgency
		scale = 12.0
	} else if daysUntil < 1 {
		// Due today
		scale = 10.0
	} else if daysUntil <= 7 {
		// Due within a week - linear from 10.0 to 6.0
		scale = 10.0 - (daysUntil * 0.571) // (10-6)/7 = 0.571
	} else if daysUntil <= 14 {
		// Due within two weeks - linear from 6.0 to 2.0
		scale = 6.0 - ((daysUntil - 7.0) * 0.571) // (6-2)/7 = 0.571
	} else {
		// Due further out - low urgency
		scale = 2.0
	}

	return scale * coeff
}

// urgencyPriority calculates urgency contribution from priority
// Order: High > Medium > Default > Low
func (t *Task) urgencyPriority(coeffs *UrgencyCoefficients) float64 {
	switch t.Priority {
	case PriorityHigh:
		return coeffs.PriorityH
	case PriorityMedium:
		return coeffs.PriorityM
	case PriorityDefault:
		return coeffs.PriorityD
	case PriorityLow:
		return coeffs.PriorityL
	default:
		return 0.0
	}
}

// urgencyAge calculates urgency contribution from task age
// Age increases linearly up to maxDays, then caps
func (t *Task) urgencyAge(coeff float64, maxDays int) float64 {
	now := timeNow()
	ageDuration := now.Sub(t.Created)
	ageDays := int(ageDuration.Hours() / 24.0)

	if ageDays > maxDays {
		ageDays = maxDays
	}

	ageRatio := float64(ageDays) / float64(maxDays)
	return ageRatio * coeff
}

// urgencyActive calculates urgency contribution for started tasks
func (t *Task) urgencyActive(coeff float64) float64 {
	if t.Start != nil {
		return coeff
	}
	return 0.0
}

// urgencyWaiting calculates urgency penalty for waiting tasks
func (t *Task) urgencyWaiting(coeff float64) float64 {
	if t.Wait != nil {
		now := timeNow()
		if t.Wait.After(now) {
			return coeff // Should be negative coefficient
		}
	}
	return 0.0
}

// urgencyTags calculates urgency contribution from tags
// Special urgent tag (configurable, default "next") has high coefficient
// Regular tags contribute with diminishing returns (0.8 for 1, 0.9 for 2, 1.0 for 3+)
func (t *Task) urgencyTags(coeffs *UrgencyCoefficients) float64 {
	tagCount := len(t.Tags)
	if tagCount == 0 {
		return 0.0
	}

	// Check for special urgent tag first
	for _, tag := range t.Tags {
		if tag == coeffs.UrgentTag {
			return coeffs.UrgentCoeff
		}
	}

	// Apply general tag coefficient with multiplier based on count
	var multiplier float64
	switch tagCount {
	case 1:
		multiplier = 0.8
	case 2:
		multiplier = 0.9
	default:
		multiplier = 1.0
	}

	return multiplier * coeffs.Tags
}

// urgencyProject calculates urgency contribution from having a project
func (t *Task) urgencyProject(coeff float64) float64 {
	if t.Project != nil {
		return coeff
	}
	return 0.0
}

// BuildUrgencyCoefficients creates UrgencyCoefficients from config
func BuildUrgencyCoefficients(cfg *Config) *UrgencyCoefficients {
	return &UrgencyCoefficients{
		Due:         cfg.UrgencyDue,
		PriorityH:   cfg.UrgencyPriorityH,
		PriorityM:   cfg.UrgencyPriorityM,
		PriorityD:   cfg.UrgencyPriorityD,
		PriorityL:   cfg.UrgencyPriorityL,
		Active:      cfg.UrgencyActive,
		Age:         cfg.UrgencyAge,
		AgeMax:      cfg.UrgencyAgeMax,
		Tags:        cfg.UrgencyTags,
		Project:     cfg.UrgencyProject,
		Waiting:     cfg.UrgencyWaiting,
		UrgentTag:   cfg.UrgencyUrgentTag,
		UrgentCoeff: cfg.UrgencyUrgentCoeff,
	}
}